This invention relates to compounds and processes for using the same to improve the dyeability of textile fibers and fibrous assemblies. More particularly, the present invention relates to quaternary ammonium compounds and processes for using the same to dye cellulosic fibers and fibrous assemblies with anionic dyes without the use of salt.
Many dyestuffs are rendered water-soluble by the incorporation of anionic groups into the dye molecule. However, the surface of cellulosic substrates is also negatively charged, and thus tends to repel anionic dyestuffs. Therefore, prior to the instant invention, virtually all dyes classified as anionic required some level of salt to speed the dyeing process.
Specifically, in a typical anionic dyeing process, the dye and the cellulosic substrate (cotton, rayon, etc.) are placed into a hot water bath, in which the cellulosic substrate swells. Salt is then added to the water to xe2x80x9csaltxe2x80x9d the dye out of solution and into the fiber. Indeed, conventional anionic dyeing processes for cellulosic fibers can employ significant amounts of salt, such as sodium chloride or sodium sulfate, as a dyebath exhausting agent. However, use of salts in dyeing can result in environmental problems relating to disposal of the exhausted dyebath.
Fiber reactive quaternary ammonium compounds have been used in conjunction with anionic dyes to increase various dyeing characteristics (such as color, color fastness, and the like). Salt free dyeing of cellulosic substrates has also been reported. For example, U.S. Pat. Nos. 5,330,541 and 5,489,313, both to Hall et al., report the use of a quaternary ammonium pretreat to eliminate salt in anionic dyeing of cellulose. In particular, the Hall et al.patents are directed to the use of an epoxy propyl trimethyl ammonium chloride pretreatment to eliminate salt in dyeing.
While these and other compounds can be useful in the dyeing of cellulosic fibrous assemblies, commercial use of such compounds has been limited. Such compounds can lack sufficient substantivity for the cellulose to provide subsequent dye color yield values comparable to those achieved when dyeing in the presence of salt. In addition, such processes can exhibit limited adaptability to various dye processes, and in particular to exhaustion or long liquor processes using conventional liquor ratios. In addition, it can be difficult to uniformly apply these compounds and/or control increased dyestuff rate-of-strike. Still further, these reagents can react sluggishly so that fixation of the compounds to a fabric must be conducted under relatively drastic conditions, for example, at elevated temperatures, high pH, and/or lengthy reaction times.
The present invention provides processes for dyeing textile fibrous assemblies having notable ecological advantages over conventional dyeing processes requiring the addition of salt to the dye-bath. Specifically, the present invention provides processes for improving the dyeability of textile fibrous assemblies containing cellulosic fibers without requiring a salt to drive the dyestuff into the cellulosic fiber. As a result, the expense, handling difficulties and disposal problems associated with salt can be eliminated. In addition, the dyes can exhaust completely to the fibrous assemblies and provide desirable deeper shades, thus maximizing dye utilization and allowing significant reductions in dyestuff usage. Further, the resulting textiles can be uniformly dyed and possess good colorfastness, thereby eliminating or minimizing the need for a fixative. Still further, the processes of the invention can be used with a variety of dyeing techniques, such as pad batch and exhaustion processes. Indeed, in contrast to prior salt-free dyeing techniques, the present invention allows the use of conventional liquor ratios in an exhaustion process. Thus the processes of the invention can also provide significant advantages in efficiency and cost as compared to conventional dyeing processes.
In the invention, fibrous assemblies comprising cellulosic fibers are treated with an aqueous composition comprising a novel highly substantive fiber reactive cationic compound of the formula (I) below: 
wherein:
R1, R2, and R3 each are independently selected from the group consisting of C1 to C20 alkyl, C5-C12 cycloalkyl, and C6-C10 aryl, each of which is optionally substituted by 1-3 halogen, amino, hydroxyl, C1-C4 alkoxy or C1-C4 alkyl; or R1 and R2, together with N, form a 5, 6 or 7 membered heterocyclic ring, such as pyrrolidine, pyrrolidone, piperidine, morpholine, piperazine and the like, or form a 5, 6, or 7 membered heterocyclic aromatic ring such as pyridine, pyrrole, pyrimidine, imidazole, nicotinamide and the like, wherein each of said heterocyclic ring or heterocyclic aromatic ring may be optionally substituted by one or more hydroxyl, amine, amide, carboxyl, carbonyl or C1-C4 alkyl; or R1, R2, and R3, together with N, form a bridged heterocyclic ring, such as quinuclidine, 1,4-diazabicyclo[2.2.2]octane (DABCO), and the like, optionally substituted by one or more hydroxyl, amine, amide, carboxyl, carbonyl or C1-C4 alkyl;
R4 is hydrogen or C1-C4 alkyl;
X is C1-C10 alkylene, preferably substituted by hydroxyl;
R5 is a 5 or 6 membered heterocyclic aromatic ring, preferably containing one or more nitrogen atoms, and having at least one reactive substituent capable of bonding with hydroxyl and amine groups;
Y is xe2x80x94NHxe2x80x94, xe2x80x94NR4xe2x80x94 or xe2x80x94Sxe2x80x94;
Z is C6-C10 aryl, C5-C12 cycloalkyl, or C2-C10 alkylene; and
An(xe2x88x92) is an anion.
Preferably, each R1, R2, and R3 is C1 to C4 alkyl; R4 is hydrogen; X is of the formula: 
wherein X1 is C1-C10-alkylene; R5 is a triazine ring substituted with at least one halogen; each Y is xe2x80x94NHxe2x80x94 or xe2x80x94NCH3xe2x80x94; and Z is benzene. In an especially preferred embodiment of the invention, the compound has the formula 
The cellulosic substrate is also treated with a suitable alkaline agent, such as sodium carbonate, under conditions sufficient to allow the pretreatment compound to covalently react with the cellulosic fibers of the fabric. The cationic reactant and alkaline agent can be applied to the fabric simultaneously or sequentially.
The fabric can then be dyed using a variety of anionic dyes, such as fiber reactive dyes, direct dyes, sulfur dyes, and vat dyes, using various dyeing techniques. Because the compounds of the invention can exhibit pronounced reactivity with hydroxyl groups of the cellulosic fibers, the compounds of the present invention can be applied under mild conditions. Accordingly, the process can be carried out at lower temperatures, lower pH values, and/or shorter reaction times than that required for prior fixing agents, such as those noted above which include an epoxy group as the reactive radical. In addition, such pretreated fibrous assemblies can be dyed using an exhaustion process with conventional process conditions. Further, the dyestuffs are substantially fully exhausted onto the fibrous assembly, resulting in a dyed material having good, uniform color and colorfastness. The remaining dye-bath effluent is substantially colorless (water-white) and free from undesirable salts, contaminants and the like.
Compounds of Formula (I) above are also provided in another aspect of the invention. The compounds of the invention can exhibit improved substantivity for cellulosic fibers as compared to traditional quaternary amines, in particular low molecular weight quaternary amines such as epoxy propyl trimethyl ammonium chloride. Due to its high substantivity, the compound can be applied to the cellulosic fibers under so-called long-liquor conditions, and the treated cellulosic fibers can subsequently be dyed with, for example, reactive dyes having water solubilizing groups such as sulphonate groups, without salt additions to the dyebath. In addition, the compounds allow use of a wider range of commercial process equipment to pretreat the fiber, while maintaining superior results. Thus, conventional dyeing procedures, equipment and routings can be used. In particular, the results achieved with the compound of the instant invention are superior to those previously possible with the use of conventional quaternary amines applied from conventional long-liquor exhaustion dyeing processes.
The present invention also provides cellulosic fibrous assemblies having a fiber reactive cationic compound of Formula (I) bound to the hydroxyl sites of the cellulosic fibers thereof, and processes for making the compounds of the invention.
The present invention will be described more fully hereinafter in connection with illustrative embodiments of the invention which are given so that the present disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. However, it is to be understood that this invention may be embodied in many different forms and should not be construed as being limited to the specific embodiments described and illustrated herein. Although specific terms are used in the following description, these terms are merely for purposes of illustration and are not intended to define or limit the scope of the invention.
The fiber reactive cationic compounds of the invention have at least two fiber reactive sites and, in a preferred embodiment, also have at least two dye reactive sites. The compounds have the formula 
wherein:
R1, R2, and R3 each are independently selected from the group consisting of C1 to C20 alkyl, C5-C12 cycloalkyl, and C6-C10 aryl, each of which is optionally substituted by 1-3 halogen, amino, hydroxyl, C1-C4 alkoxy or C1-C4 alkyl; or R1 and R2, together with N, form a 5, 6 or 7 membered heterocyclic ring such as pyrrolidine, pyrrolidone, piperidine, morpholine, piperazine and the like, or form a 5, 6, or 7 membered heterocyclic aromatic ring such as pyridine, pyrrole, pyrimidine, imidazole, or nicotinamide, and the like, all of which may be optionally substituted by one or more hydroxyl, amine, amide, carboxyl, carbonyl, or C1-C4 alkyl; or R1, R2, and R3, together with N, form a bridged heterocyclic ring, such as quinuclidine, 1,4-diazabicyclo[2.2.2]octane (DABCO), and the like, optionally substituted by one or more hydroxyl, amine, amide, carboxyl, carbonyl or C1-C4 alkyl;
X is C1-C10 alkylene, preferably substituted by hydroxyl;
R5 is a 5 or 6 membered heterocyclic aromatic ring, preferably containing one or more nitrogen atoms, and having at least one reactive substituent capable of bonding with hydroxyl and amine groups;
Y is xe2x80x94NHxe2x80x94, xe2x80x94NR4xe2x80x94 or xe2x80x94Sxe2x80x94;
Z is C6-C10 aryl, C5-C12 cycloalkyl, or C2-C10 alkylene; and
An(xe2x88x92)is an anion.
Preferably, each R1, R2, and R3 is C1 to C4alkyl; R4 is hydrogen or C1-C4 alkyl; X is 
wherein Xxe2x80x2 is C1-C10-alkylene, preferably methylene; R5 is a 6 membered heteroaryl selected from the group consisting of pyridine, pyrimidine, quinoxaline and triazine, preferably triazine, substituted with halogen; each Y is xe2x80x94NHxe2x80x94 or xe2x80x94NCH3xe2x80x94; and Z is benzene. Exemplary anions include anions of both organic and inorganic acids, and include without limitation chloride, bromide, sulfate, phosphate, tetrafluoborate, and the like. Also included are anions of acid alkyl esters of inorganic acids, such as the methosulphate and ethosulphate ions.
A particularly preferred compound of the invention has the formula 
As used herein, the term xe2x80x9calkylxe2x80x9d means straight, branched or cyclic hydrocarbon, optionally substituted with one or more substituents, such as but not limited to, 1-3 halogen, amino, hydroxyl, C1-C4 alkoxy, C1-C4 alkyl, and the like. xe2x80x9cHeterocycle xe2x80x9d or xe2x80x9cheterocyclicxe2x80x9d means a 5, 6 or 7 membered ring without aromatic character and at least one ring atom which is not carbon, optionally substituted with one or more substitituents, such as but not limited to hydroxyl, amine, amide, carboxyl, carbonyl, C1-C4 alkyl, and the like. xe2x80x9cArylxe2x80x9d means one or more aromatic rings, each of 5 or 6 carbon atoms, optionally substituted with one or more substituents, such as but not limited to, 1-3 halogen, amino, hydroxyl, C1-C4 alkoxy, C1-C4 alkyl, and the like. Multiple aryl rings may be fused, as in naphthyl or unfused, as in biphenyl. xe2x80x9cHeterocyclic aromatic,xe2x80x9d or heteroaryl, is an aryl group which can include 5, 6 or 7 members and further can contain from one to four N, O, or S atoms(s) or a combination thereof, optionally substituted at one or more of the carbon or nitrogen atom(s) with C1-C4 alkyl, or a carbon atom in the heteroaryl group together with an oxygen atom form a carbonyl group, or which heteroaryl group is optionally fused with a phenyl ring. Heteroaryl also may optionally be substituted with one or more substituents, such as but not limited to, hydroxyl, amine, amide, carboxyl, carbonyl, C1-C4 alkyl, and the like. For example, when R1 and R2, together with N, form a heterocyclic aromatic ring, the heterocyclic aromatic wrong can be a 5, 6 or 7 member heterocyclic ring. Also as an example, R5 is a 5 or 6 member heterocyclic aromatic ring. Heterocyclic aromatic includes, but is not limited to, 5-membered heteroaryls having one hetero atom (e.g., thiophenes, pyrroles, furans); 5 membered heteroaryls having two heteroatoms in 1,2 or 1,3 positions (e.g., oxazoles, pyrazoles, imidazoles, thiazoles, purines); 5-membered heteroaryls having three heteroatoms (e.g., triazoles, thiadiazoles); 6-membered heteroaryls with one heteroatom (e.g., pyridine, quinoline, isoquinoline, phenanthrine, 5,6-cycloheptenopyridine); 6-membered heteroaryls with two heteroatoms (e.g., pyridazines, cinnolines, phthalazines, pyrazines, pyrimidines, quinazolines); 6-membered heteroaryls with three heteroatoms (e.g., 1,3,5-triazine); and 6-membered heteroaryls with four heteroatoms. xe2x80x9cAlkylenexe2x80x9d includes alkylene optionally substituted with one or more substitutents, such as but not limited to, 1-3 halogen, amino, hydroxyl, C1-C4 alkoxy, C1-C4 alkyl, and the like. xe2x80x9cHalogenxe2x80x9d means chloride, fluoride, iodide or bromide.
The compounds of the invention can be prepared by condensing an amine of the formula 
wherein each R1, R2, R3, R4 and X have the meanings defined above, with a 5 or 6 membered heterocyclic aromatic compound, preferably a nitrogen containing heteroaryl compound such as a triazine, having at least three reactive substituents capable of bonding with hydroxyl and amine groups. Preferably the reactive substituents are halide, more preferably chloride. As will be appreciated by the skilled artisan, at least one of the reactive substitutes reacts with the amine group to attach the heterocyclic aromatic ring to the amino group and form a reactive heterocyclic quaternary derivative of the formula 
wherein R1, R2, R3, R4, R5 and X are as defined above. Thereafter, two molecules of the resultant reactive heterocyclic quaternary derivative are coupled using a suitable bridging compound, such as p-phenylene diamine or ethylene diamine. The bridging compound is substituted with at least two nucleophilic substituents capable of linking or coupling two molecules of the quaternary derivative via reaction with a reactive substitutent of R5 to form the multi-functional quaternary agents of Formula (I).
The reaction steps are conducted under conditions of pH, time and temperature sufficient to synthesize the compounds of the invention. Preferably, the condensing step is conducted at a pH of about 4 to about 8, more preferably about 6.5 and a temperature of about 0 to about 15xc2x0 C., more preferably about 0 to about 5xc2x0 C. The coupling step is preferably conducted at a pH of about 4 to about 8, more preferably about 6.5, and a temperature of about 30 to about 50 xc2x0 C., more preferably about 35 to about 40xc2x0 C.
The reagents (amine, heterocyclic aromatic compound and di-amino bridging compounds) can either be prepared using commercially available compounds or are known in the art. Exemplary amines include without limitation synthesized reagents such as 1-amino-2-hydroxy-3-trimethyl ammonium propane, as well as commercially available reagents such as 1-amino-3-trimethyl ammonium propane, 1-amino-3-dimethyl ethyl ammonium propane, 1-amino-3-diethyl methyl ammonium propane, and the like.
Exemplary heterocyclic aromatic compounds are noted above. Preferably the heterocyclic aromatic compound is a trihalogenated symmetrical triazine, such as cyanuric chloride and cyanuric bromide. The compound can include reactive substituents other than halide, such as thiosulphato, sulphonate, and the like. A preferred aromatic bridging group is phenyl, substituted with hydroxy, thio or amino groups as the nucleophilic substituents. Representative alternative bridging groups include aliphatic diamines, such as H2Nxe2x80x94(CH2)nxe2x80x94NH2, wherein n is 2-5; cycloaliphatic diamines, such as cyclohexane diamine; and aliphatic thio-amines, such as HSxe2x80x94(CH2)nxe2x80x94NH2, wherein n is 2-5.
In one particularly preferred aspect of the present invention, Nxe2x80x94 (3-chloro-2-hydroxypropyl) trimethylammonium chloride is first converted to its epoxide form, 2-3 epoxy propyl N-trimethylammonium chloride, by reaction with sodium hydroxide. The epoxide and its precursor are known and are commercially available from Dow Chemical Company. The epoxide is then reacted with ammonia to form the novel compound, 1-amino-2-hydroxy-3-trimethyl ammonium propane (AHTAPC), shown below: 
AHTAPC is then condensed with cyanuric chloride to yield the novel reactive dichloro-s-triazine quaternary derivative given below: 
Two of the dichloro-s-triazine molecules are then coupled together via their reaction with p-phenylenediamine to yield the novel bifunctional monochlorinated heterocyclic quaternary ammonium compound shown below: 
The water soluble, fiber reactive cationic compounds of the invention can be used in the pretreatment and dyeing of fibrous assemblies. The process is used with fibrous assemblies formed from yarns comprised of cellulosic fibers including cotton, linen, flax, viscose, cotton blends such as cotton/polyester blends, and the like. In addition, this process is also useful on other polyhydroxyl polymers such as polyvinyl alcohol. The fibrous assemblies dyed according to the invention can be greige (untreated) fibrous assemblies that have not been desized, scoured, or bleached prior to pretreatment. The process of the invention can also be used with fibrous assemblies treated to remove sizing or other processing agents. As used herein the term xe2x80x9cfibrous assembliesxe2x80x9d includes without limitation woven, nonwoven and knit fabrics, fibers, yarns, and the like.
In the process of the invention, the fabric is initially treated with a pretreatment composition comprising the fiber reactive bifunctional monohalogenated heterocyclic quaternary compound of the invention. The treating step may be accomplished by any suitable method. Preferably, the fiber reactive bifunctional monohalogenated heterocyclic quaternary compound of the invention is applied to the fabric via an exhaustion process, based on a liquor ratio ranging from about 5:1 to 50:1 and preferably about 10:1 or higher.
The compound of the invention can be applied to the fabric in amounts of about 2% to about 10% OWF (on weight fabric), and preferably about 3% to about 6% OWF. In addition, a suitable alkaline fixing agent is also applied to the fabric. Any of the known alkaline fixing agents known in the art can be used, including, but not limited to, sodium carbonate, sodium bicarbonate, sodium hydroxide, and the like, and mixtures thereof. The alkaline agent can be used in conventional amounts, typically about 5 to about 40 g/L, and preferably about 10 to about 20 g/L. The amount of alkaline fixing agent present in the pretreatment composition is sufficient to allow the quaternary ammonium compounds to penetrate the waxes, oils, and/or sizing agents which may be present on the cellulosic fibers and to promote significant ionization of the hydroxyl groups on the cellulosic fibers to form an adequate number of nucleophilic cellulosate anions and allow covalent bonding with the reactive substituents of the pretreatment compound.
The fiber reactive cationic compound of the invention and the alkaline agent can be applied simultaneously or sequentially. In one aspect of the invention, the fabric is treated with an aqueous pretreatment solution containing the fiber reactive cationic compound at a temperature from about 10 to about 100xc2x0 C. The temperature is raised over 30 units, preferably to at least about 70xc2x0 C., or higher, and held at this elevated temperature for up to 30 minutes. Alkali is then added to the bath and the fabric is maintained at a temperature ranging from about 60 to about 100xc2x0 C. for about 20 to about 60 minutes.
In an alternative embodiment, the cellulosic fibrous assembly is treated with the reactive heterocyclic quaternary derivative of formula (II). In a preferred alternative embodiment, the reactive heterocyclic quaternary derivative is the bihalogenated heterocyclic quaternary amine given in formula (III). Milder pretreatment conditions may be employed when applying the derivative of formula (III) as a pretreatment, rather than formula (I). In this alternative embodiment, fabric is treated with an aqueous pretreatment solution containing the bihalogenated heterocyclic quaternary amine at a temperature from about 10 to 30 xc2x0 C. The temperature is then raised to 40 to 50xc2x0 C. and allowed to equilibrate for 15 to 20 minutes. A sufficient amount of mild alkali, such as sodium carbonate, is then added to the bath and the fabric is maintained at a temperature ranging from about 40 to 50xc2x0 C. for about 20 to 60 minutes.
The reactive heterocyclic quaternary derivative (II) may be applied by any suitable method, including both padding and substantive application processes. Non-substantive processes include pad batch, pad dry, pad steam, spraying, or immersing.
The pretreatment composition can contain other additives as known in the art, for example, a rheology modifying agent such as an antimigrant. Suitable rheology modifying agents include high molecular weight polymers such as high molecular weight polyacrylamide polymers having molecular weights of six million or higher. In addition, the pretreatment composition can include a wetting agent. Exemplary wetting agents include soaps, alcohols, fatty acids, and other agents that facilitate the absorbance of the aqueous components onto the fabric. For examples of well-known wetting agents that may be useful in the present invention, reference may be made to Surface Active Agents and Detergents, Vol. I and II by Schwartz, Perry and Burch; and U.S. Pat. No. 4,465,619 to Boskamp. Particularly preferred wetting agents are nonionic wetting agents such as alkyl phenol ethoxylates, linear alcohol ethoxylates, and fatty acid ethoxylates. The composition may further include small amounts of other conventional additives.
At the end of the pre-treatment process, the cationized fibrous assemblies can be removed and washed to remove unreacted fiber reactive cationic compound. For example, the fibrous assemblies can be washed with cold water for about 5 to about 30 minutes, and preferably about 10 minutes.
The pre-treated, washed fibrous assemblies are then dyed with an anionic dye. Any of the types of anionic dyes known in the art can be suitably employed in this process. Preferably, the dyestuffs include at least one dye selected from the group consisting of direct dyes, premetallized dyes, acid dyes, sulfur dyes, vat dyes, pigment dyes, reactive dyes and natural dyes. The specific dyestuffs used may be selected by those skilled in the art depending upon the type of fabric used, the particular color desired and other considerations. For example, with fibrous assemblies containing cellulosic fibers, such as cotton, direct dyes, fiber reactive dyes, acid dyes, vat dyes, sulfur dyes and/or pigment dyes may be used. Examples of suitable direct dyes include Direct Red 24, Direct Red 79, Direct Red 80, Direct Blue 189, Direct Blue 191.
In a preferred embodiment, the dye employed is a reactive dye. Fiber reactive dyes are characterized by the presence of electrophilic substituents, such as double bonds or heterocyclic halogens, which react with nucleophilic groups, such as hydroxyl groups. Examples of suitable fiber-reactive dyes include monochlorotriazine dyes (Procions(copyright) H dyes from BASF), vinyl sulfone dyes (Remazol(copyright) dyes from Dystar), difluorochloropyrimidine dyes (Levafix(copyright) E-A dyes from Dystar), monofluorotriazine dyes (Cibacron(copyright) F dyes from Ciba), modified monochlorotriazine dyes (Drimarene(copyright) X-N dyes from Clariant), monochlorotriazine-vinyl sulfone difunctional dyes (Sumifix Supra dyes from Sumitomo), dichlorotriazine dyes (Procion(copyright) Mx dyes from BASF), dichloroquinoxaline dyes (Levafix(copyright) dyes from Dystar), trichloropyrimidine dyes (Drimarenes X dyes from Clariant), bifunctional monochlorotriazine dyes (Procion(copyright) H-EXL dyes from BASF) and bifunctional monofluorotriazine dyes (Cibacron LS from Ciba).
Most shades with a properly balanced formula will be fully exhausted onto the fabric. The dyestuffs may be applied by any method, including various methods of exhaust dyeing and pad dyeing, as is known in the art.
In one embodiment of the invention, dyestuffs are introduced into a dyebath on a very slow, gradual basis. Preferably, the dyestuffs are introduced over a period of at least 5 minutes. When the dyestuffs are added, the dye-bath preferably has a temperature of about 40xc2x0 C., and a liquor to goods ratio of about 10:1 or higher. Once the dyestuffs have been added, the washed, pretreated cotton fabric is placed in the dye-bath and the dye-bath is heated to its boiling temperature for time appropriate for the dye to exhaust onto the fabric. Typically, about 60 minutes is required to exhaust the dye onto the fabric. If the dye is a reactive dye, fixation is induced by adjusting the pH of the dyebath to a range of between 7 to 12, preferably 9.
In one example, Procion Red HE-3B, a fiber reactive dye, is employed at a 10:1 liquor ratio, along with sufficient 0.2 M disodium hydrogen phosphate to provide a starting pH of 9. The result is a cotton fabric, pre-treated using a long liquor process, dyed without the use of salt, which possesses a significantly higher color yield than untreated fibrous assemblies dyed with the traditional salt/alkali process. As an added benefit, use of the pretreatment compound of the instant invention allows milder dyeing conditions to be utilized with fiber reactive dyes. Conventional reactive dyeing requires a strongly alkaline environment, such as pH 10.5, to sufficiently activate the cellulose to react with the dyestuff. The present pretreatment compound provides a much more active nucleophilic site, in addition to the other benefits enjoyed from its cationic properties. This heightened nucleophilicity enables use of lower pHs, in the range of 7-9, to be used in reactive dyeing in the present invention.
In an alternative embodiment, a pretreated polyester/cotton fabric can be dyed with minor modifications to the normal disperse dyeing process to yield similar results. In the present invention, reactive dye and disperse dyes are introduced at 30xc2x0 C. at pH 7.5 and the bath raised to 130xc2x0 C. and maintained at this temperature for 30 minutes.
After the dye has been fully exhausted onto the fabric, and before the bath is drained, optional additives may be introduced into the bath. Specifically, additives such as anionic softeners, soil release agents, anti-stain agents, anti-static agents or the like can be added to the bath. The wet dyed fabric is subsequently removed from the dyeing apparatus and may then be finished by conventional methods.
The fabric which results from this process is characterized by having a cationic compound reacted with a cellulose hydroxyl group. In addition, in a preferred embodiment, the pretreatment compound, covalently bonded to the cellulosic fibers, also contains hydroxyl substituents. These pretreatment compound hydroxyl substituents are highly active and are readily available for subsequent covalent bonding with molecules containing electrophilic substitutents, such as reactive dyes having sulphonate or other electrophilic groups. Thus, in addition to cationic properties, the hydroxyl substituents of the pretreatment compound also provide reactive dye sites, which are distributed uniformly throughout the fabric. Although not wishing to be bound by any explanation of the invention, it is believed that the hydroxyl groups of the pretreatment compounds are more active, or nucleophilic, than expected, due to their close proximity to the quaternary amine substitutent on the pretreatment molecule. It is believed that the quaternary amine groups increase the ionic character of these nearby hydroxyl groups, a theory referred to as the xe2x80x9cneighboring group effect.xe2x80x9d The ability to use milder reactive dyeing conditions in conjunction with the present invention is an example of a benefit from this effect.
Although not wishing to be bound by any explanation of the invention, it is believed that the anionic dyestuffs are electrostatically bound to the modified cellulose by the ionic attraction of the quaternary amine groups to the anionic dye. This is considered especially important in the use of direct dyestuffs, which are attracted to the cellulose surface by only weak forces, such as Van Der Waal""s attraction. Reactive dyes are initially strongly attracted by the electrostatic interactions between their sulphonate group and the pretreatment cation, and diffuse out of the dyebath and into the fiber based on this attraction. After the reactive dye has penetrated the fiber, it readily reacts covalently with the highly nucleophilic hydroxyl group from the pretreatment compound, yielding enhanced fastness properties.
In addition, it has been further proposed that the strong positive charge of the ammonium group on the cationization compound of the instant invention neutralizes the negative charge on the fiber surface, which otherwise acts a barrier to the absorption of the negatively charged (anionic) dye. Due to this surface neutralization, the salt that was needed to obtain the shift is no longer required.